1. Field of the invention.
This invention relates to a valve for pinching off flow through a fluid conduit, and more particularly to a valve which utilizes a control pressure for controlling flow rate through the conduit and a method for fabricating the valve.
2. Description of the prior art.
Many types of valves exist for controlling fluid flow through a conduit. Valves such as globe valves or gate valves require precision fitting parts and seals between the inside of the valve and the exterior of the valve where the valve control passes through the valve body. The precision parts in such valves are often subjected to wear due to abrasive characteristics which may exist in the flowing medium. Where such flow characteristics exist, and/or where flow pressures are not too high, pinch type valves are known which utilize external pressures for distending a flexible internal member until it blocks the flow channel. Known pinch type valves exhibit frequent failure due to separation in the flexible member caused by pressure applied to the flexible member to obtain the necessary valve seals. Elaborate mechanisms have been required in the past to obtain the valve seals for proper flow control.
A valve is needed for use in controlling flow of any type of medium, which is not susceptible to internal precision part wear, which exhibits substantially no head loss across the valve, which provides a positive and durable seal between the flowing medium and the exterior of the valve, and which is of a construction readily adapted to an efficient method of fabrication utilizing inexpensive and readily available materials.